----- On Jun 14, 2022, at 9:39 AM, Mathieu Desnoyers mathieu.desnoy...@efficios.com wrote:
> ----- On Jun 13, 2022, at 11:55 PM, Minlan Wang wangmin...@szsandstone.com > wrote: > >> Hi, Mathieu, > > Hi Minlan, > > Thanks for the detailed bug report. Can I ask more precisely which commit ID > of the userspace-rcu stable-2.12 branch you are using ? Typically a I meant "stable-0.12" branch here. Thanks, Mathieu > "userspace-rcu-latest-0.12.tar.bz2" > gets generated from a git tree at a given point in time, but it does not give > me enough details to know which commit it refers to. > > Thanks, > > Mathieu > >> We are running a CentOS 8.2 os on Intel(R) Xeon(R) CPU E5-2630 v4, >> and using the workqueue interfaces in src/workqueue.h in >> userspace-rcu-latest-0.12.tar.bz2. >> Recently, we found the workqueue thread rushes cpu into 99% usage. >> After some debuging, we found that the futex in struct urcu_workqueue got >> into very big negative value, e.g, -12484; while the qlen, cbs_tail, and >> cbs_head suggest that the workqueue is empty. >> We add a watchpoint of workqueue->futex in workqueue_thread(), and got this >> log when workqueue->futex first get into -2: >> ... >> Old value = -1 >> New value = 0 >> 0x00007ffff37c1d6d in futex_wake_up (futex=0x55555f74aa40) at workqueue.c:160 >> 160 in workqueue.c >> #0 0x00007ffff37c1d6d in futex_wake_up (futex=0x55555f74aa40) at >> workqueue.c:160 >> #1 0x00007ffff37c2737 in wake_worker_thread (workqueue=0x55555f74aa00) at >> workqueue.c:324 >> #2 0x00007ffff37c29fb in urcu_workqueue_queue_work >> (workqueue=0x55555f74aa00, >> work=0x555566e05e00, func=0x7ffff7523c90 <write_dirty_finish>) at >> workqueue.c:3 >> 67 >> #3 0x00007ffff752c520 in aio_complete_cb (ctx=<optimized out>, >> iocb=<optimized out>, res=<optimized out>, res2=<optimized out>) at >> bio/aio_bio_adapter.c:152 >> #4 0x00007ffff752c696 in poll_io_complete (arg=0x555562e4f4a0) at >> bio/aio_bio_adapter.c:289 >> #5 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 >> #6 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 >> [Switching to Thread 0x7fffde3f3700 (LWP 821768)] >> Hardware watchpoint 4: -location workqueue->futex >> >> Old value = 0 >> New value = -1 >> 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> 490 ../include/urcu/uatomic.h: No such file or directory. >> #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 >> #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 >> #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 >> Hardware watchpoint 4: -location workqueue->futex >> >> Old value = -1 >> New value = -2 >> 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> 490 in ../include/urcu/uatomic.h >> #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 >> #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 >> #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 >> Hardware watchpoint 4: -location workqueue->futex >> >> Old value = -2 >> New value = -3 >> 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> 490 in ../include/urcu/uatomic.h >> #0 0x00007ffff37c2473 in __uatomic_dec (len=4, addr=0x55555f74aa40) at >> ../include/urcu/uatomic.h:490 >> #1 workqueue_thread (arg=0x55555f74aa00) at workqueue.c:250 >> #2 0x00007ffff72e6ea5 in start_thread () from /usr/lib64/libpthread.so.0 >> #3 0x00007ffff415d96d in clone () from /usr/lib64/libc.so.6 >> Hardware watchpoint 4: -location workqueue->futex >> ... >> >> After this, things went into wild, workqueue->futex got into bigger negative >> value, and workqueue thread eat up the cpu it is using. >> This ends only when workqueue->futex down flew into 0. >> >> Do you have any idea why this is happening, and how to fix it? >> >> B.R >> Minlan Wang > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
